processPrompt abstract method
Process a command line as if entered interactively.
This is the primary entry point that routes to all other functionality. Supports all REPL commands and maintains multiline state.
Multiline Support:
Multiline mode is tracked in the CLI state. When .start-* is called,
subsequent processPrompt() calls accumulate in the multiline buffer
until .end is called.
Returns the result of the command, or null for commands with no output. Throws CliException for errors.
Example:
cli.processPrompt('classes'); // Single command
cli.processPrompt('.start-script'); // Enter multiline mode
cli.processPrompt('var x = 1;'); // Accumulates
cli.processPrompt('.end'); // Executes multiline block
Implementation
Future<dynamic> processPrompt(String line);